Implantable medical devices include, among other things, cardiac rhythm management (CRM) devices such as pacers, cardioverters, defibrillators, cardiac resynchronization therapy (CRT) devices, leadless pacing seeds, as well as combination devices that provide more than one of these therapy modalities to a subject. Such implantable devices are typically powered by a battery. As the battery's useful life becomes exhausted, the implanted device may malfunction, causing errors in the therapy it provides and/or its communication with other devices.